According to the passage, which is true about the ocean?
A. The waters of the ocean came from rain water.
B. The ocean was formed from the, lighter rock materials.
C. The vast single ocean formed about 200 million years ago.
D. The ocean covered the whole surface of the earth at very beginning.
______ a river on land, an ocean current does not flow in a straight line.
A.Alike
B.Like
C.Likewise
D.Likely
According to the passage, primitive ocean life begins to evolve into complex organisms
A.in the middle of December
B.when Earth is cratered
C.at the beginning of November
D.when the land is still a lifeless waste
Now scientists know ______.
A.what makes people feel cool near a lake or a river in summer
B.everything about the ocean
C.why the ocean does not get more and more salty
D.what happens to the salt in the ocean
根据以下内容回答题:
A tid.al wave is a very large and very destructive wall of water that rushes in from the ocean toward the shore.Many scientists call these huge waves tsunami(海啸).In Japanese tsunami means“storm wave”0r“tide”.But do you know that tidal waves are not caused bv storms and that they are not true tides at all?A true tide is the regular rise and fall of ocean waters,at def-inite times each day.But a tidal wave comes rushing in suddenly and unexpectedly.A tidal wave is caused by an underwater earthquake.Scientists call the underwater earthquake a seaquake.The word“seaquake”is made up of two words.the word’“sea”which means“ocean”and the word“quake”.To quake means“to shake”or“to tremble”.When a seaquake takes place at the bottom of the ocean,the ocean floor shakes and trembles,and sometimes the ocean floor shifts.It is this shifting that produces the tidal wave.The tidal wave begins to move across the sea at great speed. Tidal waves have taken many human lives in the past.Today scientists can predict when a tidal wave will hit land.They use a seismograph to do this.A seismograph is an instrument that records the strength,the direction,and the length of time of an earthquake or seaquake.It is not possible to hold back a tidal wave,but it is possible to warn people that a tidal wave is coming.This warning can save many lives.
According to the article,what causes a tidal wave?
A.The rise and fall of ocean water at regular times.
B.Seaquakes.
C.Storm.
D.The great speed of the ocean waves.
A. the high mountains
B. the lighter rocks
C. the vast ocean
D. the great continent
According to the passage, the earth in its very early period was ______.
A. in molten state
B. in water state
C. in rock state
D. a vast ocean
Computers in the future could be used to ______.
A.predict new educational achievement
B.make tourism more successful
C.help people have a bright look at tomorrow
D.travel to the ocean floor to study it
According to the passage, magnesium was first obtained from ______.
A.rocks found on land
B.great amounts of ocean water
C.the sea floor
D.major industrial sites